Treatment of distillate fuel oils with aqueous anti-microbial agents



TREATMENT OF DISTILLATE FUEL OILS WITH AQUEOUS ANT I-MICROBIAL AGENTS Henry A. Ambrose, Penn Township, Allegheny County,

Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporationof Delaware No Drawing. Filed Dec. 30, 1955, Ser. No. 556,412

3 Claims (Cl. 44-72) This invention relates to treatment of distillate fuel oils with aqueous anti-microbial agents, and more particularly to treatment of distillate fuel oils that tend to deposit gels due to gel-forming microorganisms.

Numerous East Coast marketers of distillate fuel oils have, in the recent past, received growing numbers of complaints on account of malfunctioning of distillate fuel oil burners due to accumulations of gelatinous deposits in fuel lines, strainers, burner nozzles, filters, needle valves, level controls, and the like. In numerous instances physical removal of the gelatinous deposits has failed to provide more than temporary relief, with the result that further service calls have been necessary to remove additionalgel deposits, often within as short a time as 7 days or less. Thus, many burner installations showa history of repeated service calls due to gel deposits within the course of a single heating season.

As an indication of the seriousness of this problem it may be noted that a recent survey of distillate fuel oil burner installations in a region where complaints due to gel deposition have been received in the past indicated that malfunctioning of the oil burners due to gel deposi tion might be expected at some time in the reasonably foreseeable future in two-thirds of the installations examined. Because of the novel appearance of these fuel oil gel deposits and because of their-persistence in the face of ordinary methods used to combat fuel oil deposits such as sludge, and because of other factors, it has been recognized that the problem of fuel oil gels is new and 'distinct from previous problems of distillate fuel oil deposits.

Systematic attempts to trace the cause of fuel oil gel deposits to an entirely chemical source, such as for example, chemical impurities, degradation or decomposition of one or more of the petroleum components of the fuel oils, or to chemical additives included in the fuel oil to improve one or more of its properties, have not been successful.

It has now been found that these fuel 'oil gels are of microbial derivation, and that they are caused by gelforming microorganisms in the fuel oil as such and/or in water entrained by or contacted by the fuel oil. It is my belief, based on microscopic examination of cultures of test samples, that an important source of infection of the entire distillate fuel oil production in a typical refinery isthe wash-water used in aqueous refining, following distilla-tion, of a minor proportion of the over-all distillate fuel production. It is not con sidered likely that the oil is contaminated prior to distillation, since the high temperatures and steam stripping to which the oil is subjected during distillation would tend, to disinfect the oil. On the other hand, it has been discovered that the water used in the conventional water! washing of distillate fuel oils that have been previously treating with aqueous treating reagents, for example aqueous caustic soda (sodium hydroxide) solution, as well as the water used in preparing the aqueous treating reagents, themselves, can contain microorganisms of States Patent the kind found in fuel oil gels and/or spores thereof. It should be noted that water that contains an extremely minute concentration of living gel-forming microorganisms or spores can constitute a very effective source of infection of distillate fuel oil, since such microorganisms exist as a substantially pure strain in distillate fuel oil and are therefore free to thrive, whereas their development is undoubtedly repressed in water due to the presence of other microorganisms and a relative scarcity of substances necessary to their existence.

The present invention is directed to a process for the reduction, at low cost, of gel deposition in the overall refinery production of blended distillate fuel oils. The process includes the step of distilling at least two fuel oil fractions boiling in the distillate fuel oil range, one of said fractions being inferior to the other in at least one characteristic. The process further includes subjecting at least a portion of the inferior of said fuel oil fractions to an additional refining treatment involving first intimate contact thereof with a minor proportion of a liquid phase aqueous refining agent that is capable of improving the inferior characteristic of the inferior fuel oil fraction, separating the treated fuel oil fraction from the partially spent aqueous refining agent, and then water-washing the oil with wash-water, wherein the water used in at least one of said aqueous refining agent and said water-washing contains fuel oil gel-forming microorganisms. The present invention includes in combination with the foregoing procedure the steps of incorporating in the wash-water, in microbicidal proportion, an oil-insoluble anti-microbial agent that is effective to destroy gel-forming microorganisms, said incorporating being effected prior to said water-washing, and after said water washing, separating washed, treated oil from the wash-water, and combining the washed, treated oil with the superior of said fuel oil fractions to form a blended distillate fuel oil that approximates the superior of said fuel oil fractions with respect to said characteristic and that has a reduced tendency to deposit gel due to gel-forming microorganisms.

The present invention will normally find use after fuel oil tanks and the infected fuel oil stored therein have been disinfected, although it can also be used with somewhat reduced effectiveness when storage tanks contain fuel oil that is infected with substantial proportions of gel-forming microorganisms. When used following disinfection of fuel tanks, the present invention will be useful in preventing further infection of the over-all distillate fuel oil production by disinfecting a distillate fuel oil component that is responsible to an important degree for infection with gel forming microorganisms of the over-all refinery production of blended distillate fuel oils. By disinfecting only the wash-water used to wash that portion of the over-all distillate fuel oil production that is refined with an aqueous reagent, as opposed to disinfecting the entire supply of water used in refiningthe fuel oil, and/or as opposed to disinfecting the entire distillate fuel oil production, a disinfected fuel oil is pro duced at minimum cost. By destroying the gel-forming microorganisms before they have had a chance to multiply in the fuel oil, one can usually. employ relatively lower concentrations of the antimicrobial agent.

Although the effectiveness of the present invention is .in substantial part connected with the destruction of gelforming microorganisms in the distillate fuel oil that is subjected to refining with aqueous refining agents, and in the wash-Water used in conjunction therewith, before the microorganisms have had a chance to multiply and/Ior 1: washing and/or that subsequently. enter. or, that; staph "the crude sample of originally removed fromzthezburner -installationto 120 F. and then filtering thro'ugh aINo. 45.

I Analysis, Spectrographicfnpm. Sam- Ash (Max. Temp.

- Analysis, Spectrographic:

Aluminum .readypresentin the fuel oil components with which the disinfected fraction is blended. Non-disinfected fuel oil fractions can become infected with gel-forming microorganisms, .for example, by.contact "with infected water :leaking :into the ,oil from defective water-cooled icon :densers, by .contact with air, "or .,-in .Other ways. :destruction f igel-forming microorganisms nsubsequent The to the aqueous refining -proc edure Eis iefiected hy the normal entrainment in theafueluoih subsequent to waterwashing, of small droplets of wash-water containing the 10 anti-microbial :agent. These wateridroplets will remain in the washed ,oil. after :blending with .other distillate .fuel

oil components, where they v:will -function to .destroy :gel-

;forming microorganisms {that are:contactedabyisaidedrop- =lets; orithese droplets may settle .outdntoian aqueous. layer at the bottom .of the, oil storage gtanks, where the anti- .FIIllCIOblfil agent contained-in tthe droplets. will function :to inhibit growth'of gel forming,qnicroorganisms ,in:the

:aqueous 'layer. It isstoqbe -noted that the dispersionin :the fuel oil ofanti-microbial: droplets -will normally .tend

to ,produce a more sterile :fuel oil than will treatment .of the aqueous layer alone. V a

The fuel oil ,gels 'with which this invention is con cerned have been found to .occur mostly in .the form of beads and films. Occasionally, howeverpthegehde- .lPOSitSv are in fibrous form. Thefueloil gels have some- .times been found to :beclear and yellowish inicolor, but :more ,often they are dark colored, thiscolor possibly being caused by Icontaminationrof theggel withhlack z-fuel oil 'sludgeor other.minutemarticles-of debris nor- 30. .mally Ipresentin .thetfuel .oil.

Chemical analysis of a large number of .samples 10f rated from concomitant fuel oil and sedimenti'by heating 1'2 Whatman filter paper."

i Gel'iFrorn Gel From Separated Gel 1 *Burner ,Burner Installation. Installation Yellow-Green" Gel. 1

Sulfur, Bomb, Percent Mercaptan Sulfu PercenL Phosphorus, Percent Nitrogen, Percent -tt. Water, p.p.m., KarlFischer.lVIetl1od 1 pH Value, Glass, Calomel Electrode- Percentu iThe gel sample from lnstallation Balsoindicated the V r presencejofthe commercial fueloiL-sludge inhihitonem- V -;:ployed inthe fuel oil;- ',The1geli sample 'from- -,Installation ri gels; the sirlfur content s:

.wasrnot .tesjted for the presence,ofqsludgeiinhibitor.' With respect-to thef moreisignificantcomponents: of.=:the

mamas for the-apparengpurity of the strain.

new mr i ly liprobably tra'ceablerdirectlycor 7Q einsnfa-r indirectly to the sulfur content of the distillate fuel on. Whether sulfur accelerates or is essential to gel deposition has not been definitely determined. However, it may be significant that the problem of gel deposition has followed the manufacture of distillate fuel oils from crude oils of relative1y:high :sulfur content. The water content of the gels isprQbablytraceabIe to moisture entrained :in the i fuelqoil. Experimental evidence indicates that water-tends-topromote=gel formation. The copper .present inthegels appearsto ,be traceahleto copper fuel feed lines in.burnerginstallations orzto the copper orhrass parts. ofi'floats, valves, :screens, 01' other :coppencontaining parts of the installations. 7 Experimental evidence also indicates thatcoppertends to promote fuel 'oilvgel deposits. g e a A systematic investigation of a large number of samples enceof an-zapparently pure strain of'livingmicroorganism,

"and alLavailable evidence points to these microorganisms gas thecauseof theiuel oil gels. ltis somewhat surprising to find that:any-mircoorganisms.cansurvive and'multiply in the fueltoil, whichrn-ay-account, at least in part, Moreover, it has heen found thatYa -geL- canheproduced in incubated samples-of previously sterilized fuel oil by inoculation of the -fuel-pilmith asmall amount of .thegel-fonming microorganisms taken fr om oil" burnerinstall-ations containing ,fueLoil gel deposits. lt has alsoj heen.founcl-thatithe. addiivelopment-iofrthe gels. Furthermore, when. a piece of Icopper wire iisfplaced in the fuel .oil, -gel formation apepears to he mmmoted; .Gel formation appeared -,to :be .'espeoiall y :favored.in fuehoilsamples that-had been inoculated with gel-forming microorganisms eandqthat were :maintained; inicontact; h both metallic copper and wa V ;ter';,containing:organic:matter cap able. of supporting miecrohialglifeh Nfltether;thetfuel, oil gels as; such are produced by zthe'imicroorg-anisms, or whether vthe micro- -;:orga'nisms;or substances; produced thereby :merely transdorm :fuel dil components, and/or :materials '-contained thereinoo .contacted'athereby to :gelrforming material The :latter possibility-would-seem to find :1, otne supporttinq the 'factzthatzgels resembling those found .iinuthe field:have1beennprep ared in :the laboratoryifrom rat-mixture ofrdodecylgand xylyl meroap-tans and n11.50111- :;ble coppermaphthenate. r l

- 1: Under iamagnificationof, 43 0 tirnes, the fueloiLglelforming microorganisms appear as a mass of multicellnlar afilame'nts. Z'Iheafilaments, show, branching, and. there is rde'nce of reproduction'by.budding. These; character'- esuarestypical :of yeast-like microorganisms. v

The exact identity of .thesergel-formmg m croorganisms FI-IS Idiflicultitoascertaingand therefore the inv ention is not limited toany: specific scientific class of microorganisms named herein. The fuel oil gel-forming mircoorganisms may. besspeciesco'f sulfurrutilizingfilamentous-bacteria of 5 the -Be ggiatoaceae family,...e.g.,n Beggiatoa, as. might. be suggestedibyithe.consistent presence of sulfur in the gels. I-Idwever,:available.evidence issconfiicting as to whether 1 the fuel en g'el forming:rnicroorganisms:thrive in contact with sulfur. xThe'possihility: that .the' gel-forming microorganisme are -jof the'Beggiatoaceae family would appear 'forrriingamicroorganisms appear i under .magnificationias 'crjographs r of the 1 gel-forming 'microorgaiiisms how ,particul-arly-.-rnarkedsimilarity,to those'of a m icronannies fprghlemiscans mi th p x I ldcntifiedas a speciesof MQnilia. The, f-act,thatig n e trains ofthe gcnus'Monilia are known utoiormemucous or gelatinous masses. maybe significantv Arm in l in A r .WIV

As already indicated, the present invention is applicable to distillate fuel oil manufacturing procedures wherein a portion of the over-all fuel oil distillate that is relatively inferior with respect to some characteristic, for example, acidity, mercaptan sulfur, or the like, is refined with a liquid phase, aqueous treating reagent that is capable of improving the fuel oil with respect to said characteristic, and wherein treated fuel oil distillate is then separated from partially spent aqueous treating reagent and then waterwashed, and wherein the water used in at least one of said aqueous treating reagent and said watenwashing contains gel-forming microorganisms, and wherein following the refining of said portion of the distillate fuel oil with aqueous treating reagent, the treated, washed portion is blended with another portion of distill-ate fuel oil that has not been refined with, said aqueous treating reagent, and that is superior to the untreated portion with respect to said characteristic, thus forming a blended distillate fuel oil that approximates the superior portion with respect to said characteristic, and that has a reduced tendency toward geldeposition. For example, the method of reducing geldeposition disclosed herein will be useful when used in conjunction with the water-wash that follows aqueous caustic soda refining o-f distillate fuel oil that has a relatively high acid number due to the presence of a relatively large proportion of acidic substances, such as naphthenic acids. An example of a distillate fuel oil having a high acid number is a straight run fuel oil distillate obtained from a crude oil produced in Southern Louisiana. A total acid number of. 0.2, which is above typical manufacturing specifications, is not unusual in such distillate.

In the neutralization of distillate fuel oils that have high acid numbers with aqueous caustic soda, the acidic fuel oil distillate is normally contacted with a quantityof caustic soda, in aqueous solution, which is greater than that theoretically required to neutralize the acidic substances in the oil. After the caustic soda contacting is complete, partially spent caustic soda solution, that is, caustic soda solution of reduced basicity, isseparated from the neutralized oil and the latter is then washed with water to remove dissolved salts, soaps, and entrained caustic soda solution.

Aqueous caustic soda refining is also useful in reducing the mercaptan content of distillate fuel oils, whether or not the caustic treating is carried out in conjunction with a mercaptan solutizer or extracting agent, such as sodium isobutyr-ate, and the herein disclosed method of reducing gel deposition in distillate fuel oils is useful in such processes when combined with the water-wash that conventionally follows separation of partially spent caustic from aqueous caustic soda treated fuel oil. In such processes, acidic substances such as n-aphthenic acids will also be neutralized by the caustic soda treatment.

In any event, the refining of distillate fuel oils with liquid phase, aqueous caustic soda solution, either for the purpose of reducing the acid number of the fuel oil,

, and/or for thepurpose of extracting mercaptans, is conventional. In general, such processes are carried out by contacting the distillate fuel oil with about 2 to about 20 percent by volume of about Zfbto 40 B. aqueous caustic soda at atmospheric pressure and at temperatures between ambient atmospheric temperature and 210 F. Any

conventional mixing apparatus designed to produce a high degree of intermixture of immiscible liquids can be used in the caustic soda contacting. For example, there can be used a vessel adapted for countercurrent flow and containing a system of baffles. The use of strong caustic soda solution, e.g., 35 f B., is not uncommon, especially 1 where ernulsification during water-Washing is not severe,

but rather dilute caustic soda solution of about 2 to l0 B. is often preferred in order to obtain a high degree of. contact with the oil. Elevated temperatures are often desirable, since they tend tofacilitate separation of the contact thereof with doctor solution.

, solution, salts and other water-soluble materials.

contact of the oil with aqueous caustic soda solution. partially spent caustic soda solution is separated by gravity settling, centrifuging or other equivalent conventional means designed to utilize differences in densities and the substantial immiscibility of the materials being treated.

After separation of neutralized oil, the neutralized oil is then water-washed in either a single stage or a plurality of stages, usually with about 10 to 200 volume percent water, to remove inorganic salts, soaps, and entrained, partially spent caustic soda solution. Any conventional apparatus, adapted for either countercurrent or concurrent flow that is designed to obtain a high degree of intercontact, can be used for said water-washing. For example, spray-washing can be used. In this method, water is added to the oil in fine streams without agitation;- as H the individual drops are relatively large, they tend to settle quickly. The spray is continued until a large portion of the soaps, salts, etc. are removed from the oil.

Notwithstanding the unusual eifectiveness of the present invention in conjunction with aqueous caustic soda refining of distillate fuel oils, the present invention is not solely applicable to such refining procedures, but it can also be used in other liquid phase aqueous refining procedures that are terminated by water-washing. An example of a distillate fuel oil refining procedure involving aqueous treating reagents, other than aqueous caustic soda, is the doctor sweetening process wherein sour, that is, mercaptan-containing, fuel oils are sweetened by converting the mercaptans to alkyl disulfides. According to conventional plant practice, sour fuel oil is sweetened by contact with about 1 to 2 volume percent of doctor solution, at atmospheric .pressure and at temperature ranging from ambient atmospheric temperature to about 210 F. Elemental sulfur, in an amount'sufficient to convert the lead mercaptides produced during the sweetening process to alkyl disulfides and lead sulfide, but not more than about 10 to 20 percent in excess of this amount, is provided in the sweetening reaction. The elemental sulfur may be furnished to the reaction in part or entirely from the elemental sulfur content of-the fuel oil or from an external source. It is normally considered the better practice to add elemental sulfur to the sour oil before Doctor solution, as is known, comprises sodium plumbite,-which can be conveniently prepared by approximate saturation of an aqueous caustic soda solution, usually about 6 to 30 B., with litharge. After the sweetening reaction is complete, the partially spent doctor solution is separated from the sweetened oil, and the latter is washed with water, usually 10 to 200 volume percent, to remove partially spent doctor Contacting methods, conditions and apparatus for docto'r treating are similar to those used for aqueous caustic soda refining.

In the application of the herein disclosed method of reducing gel deposition to the aqueous refining of distillate fuel oils, an oil-insoluble anti-microbial agent that is effective to destroy the fuel oil gel-forming microorganisms will be dissolved in microbicidal proportions v in the water used in the water-washing of the distillate the fuel oil during some earlier stage of the refining process, for example during the prior contact of the on with aqueous caustic sodaisolution, doctor solution, or

.oil from partially spentcau'stic soda; solution. Following 775' the like r 1.

l'-.-bythe :aqueous refining agent. portion .of fuel: 'oil distillate that hasan-acid' 'number 'or sameness use' of 'an anti-niicrbbial agent of the kind 7dis closed herein in the -waslrwater is advantageous in that 'esuch-use substantially =avoids any problems of chemical compatibility -and/or of-reduced etfectiveness- -of' the:antiamicrobial agent dueto adverse efiects of the fuel oil treating reagent thereon. Moreover, the use of the-antimicrobial-agent in the-wash-water only,-- rather than-also Lin'the water :usedeinpreparing the aqueous treating --reagent, or in theentirewater supply, minimizes :ihe cost ot -effectively treatingdhe aqueous-'-agent-refined distillate distillate fuel oil. It is, of course, unnecessary in conventional refinery practice to subject all of the distillate:fuel oilproduction toaqueous refining procedures of the type disclosed herein. -Rather, itis customary merely to treat that fraction of the-total refinery production of distillate fuel oil that does nOtmeet-manufacturing specifications with. respect to some characteristic that can'be improved For example, only .that

:mercaptancontent above specification limits, orso' much -ofthat portionas-is necessary to treat in order'for the iblended product to have-satisfactory properties, will -be "subjected"to aqueouscaustic so'dacontacting.

As previously indicated, according to my invention,

theportion of over-all refinery product ofdistillate fuel 'oilthat has been refined with an aqueous treating reagent 1 and that has been washed with water containing anii crobicidal proportion of an anti-microbiaPagent effective 1, to destroy -gel-formingmicroorganisms, is blende'd with a'dditional distillate fuel oil-that'has not been refined with the aqueous treating agent and zwater-washed, in order to produce a blended distillate-fuel oil that approaches saidadditional distillate fuel oil with 'respect' to the char- .acteristic that has been improved'byaqueous refining, sand that exhibits reduced tendencies toward gel-deposition dueto gel-forming microorganisms. It is again noted that distillate fuel oils that are exposed toQjgel-forming EmiCI'OOl gaHiSmS after treatment according to this invention, whether or notthey have been blended'--with"other "ifllels oil ;components, w'ill possess *reduced geLforming atendencies,becauseofthe carry-over in such" oils of .drop- 'zalets-iofr wash-water thatcontain an anti-microbial, agent.

. rslAnti-microbial "agents that are suitable for 'the {pun poses of this invention are those thatare' cap'able of :-:.destroying or killing the fuel oil gel-forming. microorganisms, that are substantially insoluble inthedistillate fuel oil that is treated thereby and thatcan be'dissolved in water. :Anaexample of. an anti-microbial agentthat'has; been. found tobe especially efiective 'for'the purpose's'of" :this; invention; particularly in conjunction with aqueous eaustic .sodajrefining processes, is the-sodiumsalto'f 2,4,5-

trichlorophenol, marketed under the name DoWicide 'B .bL=.l1hQ;DDW Chemical Company. DowicideB is-soluble.

V -in-waterinthe;proportion.of"1 13 grams per 100 gr'ams 6 of zwateriat C.,- and itis onlyslightlysoluble -in 'No. :2

: fuel o'il. "This agent has been-found effective to: destroy igelforming:microorganisms :inconcentrations as low as .:one part in 80,000. Other water-soluble, substantially fuel oil-insoluble anti-microbial agents gwhichihave been. v

found etfective vfor the --purposes offthis inventiontare m ixed gallgyltolylmethyl '-;trimethylainmonium (chlorides niixed 1alkyldimethylbenzlyammonium l chlorides wherein .the-alkyl groups are :C H .to C H (marketed as Roccal by :Sterwintchemicalacompany). "Hyamine .2389 and Roccal have beenafoundefiectivezwhennsed in concentrations respectively? of one.partin- ;000 .andone part in 10,000. -However,zthe invention"is not "limited "to the .usezof;theiabove=specifid. "anti-microbial agents,

and other -anti-microbial:agents capable. of killing gelforming microorganisms,:..that are. substantially insoluble 10 in? distill-ate fuel oil, :and thatv cansbe. dissolved in Water,

can be used. Although the action :of theanti-rnicrobial agents upon thelgel+formingmicroorganisms with .which this invention is concerned is selective, other suitable antimicrobial agents canbe determined by means of suitable lfilaboratory. scale tests. :Accordingtooneisuitable test,

. there isfirst preparedsa solution containingthe rantimicrobial agent thatis .tolbe tested,:usually one part of the anti-microbialagent (by weight, if solid; byivolume, .if liquid) per parts of water. To a'nutrient medium capable of supporting the growth of :the gel-forming microorganisms there is then added a quantity. of the solution of the anti-microbial agent that will produce the desired test concentration ofanti-microbial'agent in .the resulting mixture. .A ;.commercial nutrient medium, 25 marketed as Mycophyl- Broth, by the Baltimore Biological Laboratories, has beenfound effective to: support. growth of the gel-forming-microorganisms. 'Ihis.materialisa solution of polypeptone and: dextrose havingapH of 7.

' The resulting solution of anti-microbial agent in the nutri- 30 cut medium is then :inoculated with a'stock culture of gel-forming microorganisms. 'The resulting mixture is 'then incubated at .20 C. for r60 days. If the microorganisms. show no evidence ofgrowth after '60 days,

the agent is regarded as effective, in the concentration tested, for use in the process disclosed herein. However,

in order to increase contact of microorganismsand antimicrobial agents, and/or in instances where'the efiective- ,ness of the anti-microbialagent tends to be reduced by the traces of spent aqueous refining agent,-soaps or salts in the. wash-water, it may be desirable to employ concentrations of the anti-microbial agent that are from'two to four times as great as those indicated as useful by the above-described test.

The additionof smallamounts of anti-microbial agents of the type disclosed herein to the-wash-w'ater used in washing distillate fuel oils that have been subjected to aqueous refining will ordinarily produce satisfactory results. The anti-microbial agents of this invention' 550 should be used in concentrations-thatare effective to destroy the gel-forming microorganisms, i.e., in microbicidal proportion. the anti-microbial agents of this invention may, of course, vary with the nature of the individual agents themselves and-possibly in some'instanees according to the :degree of infection of the fuel oil," and/ or the water used in aqueous refiningfthereof; with "gel-forming microorganisms.f In general, within these limits effective results willbe obtained by dissolving in :"thefwa'sh-water anti-microbial agents of thekind disclosed herein. in amount-df'between about 0.001 andabouty0.1 percent. gNormally, "concentrations of about 0.005 to about "0.05 will be preferred so as to obtain a good 'balance between econ omyand eifectiveness of'results. Howe'vn-"in individual instances, for example, 'those-where the water used in aqueous refining of thefueloiljnvolvesa relatively low degree of infectio'nof gel-forming microorganismsand/or relatively highly ieifective anti-microbial agents, "concentrations" of antimicrobial agents as low -as -0;001 percent; or'possibly instances, for- -example-,*whre the waterus'ed -in- 'aqueous 1 refining involves a' relatively-" high de gr'ee" ot-infection l and/or: a relatively less'active antimiicrobiaFagent; cons egentrations' ofanti-microbiakagent df' pi l percent; or 1 flfi' 'pqssibly-morep mayi be?desirablei;

The optimum concentration of Fuel oils that can be treated according to this invention are those distillate fuel oils that tend to deposit gels due to the presence of gelforming microorganisms and that are subjected to refining with an aqueous treating reagent and wash-water, at least one of which contains gel-forming microorganisms. A specific example of a fuel oil, the treatment of which is included by this invention, is No. 2 fuel oil, a type of distillate fuel used for domestic heating and light industrial heating purposes. A No. 2 fuel oil is defined in the ASTM Standards on Petroleum Products and Lubricants, under the specification designated D-396-48T. Specific examples of other distillate fuel oils included by the invention are diesel fuels and No. 1 fuel oil. It is noted that the problem of gel formation due to microorganisms appears to be restricted to distillate fuel oils. The reason for this apparent selectivity is not certain, but it may be due to the characteristically high sulfur content of these fuel oils, or it may be due to the nature of the conditions under which these oils are used. Thus, these oils are normally used in installations involving relatively long term storage in contact with water and copper.

The terms microbial, anti-microbial, microbicidal and the like are used herein in their broader sense and as such have reference to microbes or microorganisms generally, whether or not they are pathogenic.

Example In a specific embodiment of the herein disclosed invention, 13,000 barrels per day of a catalytically cracked No. 2 fuel oil distillate boiling between about 350 and 650 F., and having a total acid number of about 0.1, is pumped, following distillation, to a blending tank, together with 2,000 barrels per day of a South Louisiana straight run No. 2 fuel oil distillate boiling in the same range and having a total acid number of 0.21. Five thousand barrels per day of the same South Louisiana straight run fuel oil distillate is passed while still warm from distillation into a caustic contactor where it is intimately contacted at atmospheric pressure with aqueous caustic soda solution, at ambient temperature, in the proportion of 640 barrels per day. The caustic soda solution is made up by diluting 11 B. caustic soda concentrate with water that contains gel-forming microorganisms in the ratio of 40 barrels of caustic concentrate (11 B.) for every 600 barrels of water. The mixture of neutralized distillate fuel oil and partially spent caustic soda solution is removed from the caustic contactor to a settling tank. Partially spent caustic soda solution is withdrawn from the bottom of the settling tank. Neutralized fuel oil distillate is withdrawn from the top of the settling tank and spray-washed, at atmospheric pressure, and at ambient temperature, with 1667 barrels per day (33.3 volume percent) of the same water that was used to dilute the caustic soda concentrate, but to which there has been added a percent aqueous solution of the sodium salt of 2,4,5-trichloropheno1 at the rate of 35 gallons per day. After water-washing, the washed fuel oil is allowed to settle, whereupon separated water is drawnoff, and the neutralized, washed oil, containing entrained droplets of water that in turn contain dissolved sodium salt of 2,4,5-trichlorophenol, is blended with the catalytically cracked No. 2 fuel oil'and the unneutralized South Louisiana straight run No. 2 fuel oil distillate referred to previously. According to the procedure described, 20,000 barrels per day of No. 2 fuel oil distillate having a total acid number of about 0.1 and having a substantially reduced tendency to deposit gels will be produced.

The foregoing example is illustrative only and other procedures involving refining of distillate fuel oils with aqueous treating reagents and water-washing of a portion of the over-all refinery production of distillate fuel oil can be adapted to the present invention. For example, in place of the South Louisiana straight run fuel oil distillate of the foregoing example there can be substituted an objectionably sour West Texas straight run fuel oil distillate, and for the aqueous caustic soda there can be substituted 2 percent by volume of doctor solution prepared by dissolving 1.5 percent litharge in a 16 B. sodium hydroxide solution. In place of the sodium salt of 2,4,5-trichlorophenol there can be substituted equivalent proportions of mixed C alkyltolylmethyltrimethylammonium chlorides and mixed C alkyldimethylbenzylarnmonium chlorides.

Obviously many modifications of the invention hereinabove described may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the claims appended hereto.

I claim:

1. A process for refining distillate fuel oil, comprising providing at least two fuel oil fractions boiling in the distillate fuel oil range, one of said fractions being inferior to the other in at least one characteristic that can be improved by aqueous refining, subjecting at least a portion of the inferior of said fuel oil fractions to an aqueous refining treatment comprising first, intimate contact thereof with a minor proportion of a liquid phase aqueous refining agent that is capable of improving the inferior characteristic'of the inferior fuel oil fraction, separating the treated fuel oil fraction from the partially spent aqueous refining agent, and then water-washing the oil with wash-water to remove water-soluble substances from the treated oil, wherein the water used in at least one of said aqueous refining agent and said water-washing contains fuel oil gel deposit-forming microorganisms, and prior to said water-washing, incorporating in the wash-water, in microbicidal proportion, an oil-insoluble, anti-microbial agent that is effective to destroy said gel deposit-forming microorganisms under conditions of pH, temperature and nutrition favorable to their growth, and after separation of the washed, treated oil from wash-water, blending the washed, treat ed oil with the superior of said fuel oil fractions to form -a blended distillate fuel oil that approximates the superior of said fractions with respect to said characteristic, and that has a reduced tendency to deposit gel due to gel deposit-forming microorganisms.

2. A process for refining distillate fuel oil, comprising providing at least two fuel oil fractions boiling in the No. 2 fuel oil range, one of said fractions being inferior to the other in at least one characteristic that can be improved by aqueous refining, subjecting at least a portion of the inferior of said fuel oil fractions to an aqueous refining treatment comprising first, intimate contact thereof with about 1 to 20 percent by volume of an aqueous alkaline solution of an inorganic refining agent that is capable of improving the inferior characteristic of the inferior fuel oil fraction, separating the treated fuel oil fraction from the partially spent aqueous alkaline solution of said inorganic refining agent, and then waterwashing the oil with 10 to 200 volume percent washwater to remove water-soluble substances from the treated oil, wherein the water used in at least one of said aqueous alkaline solution and said water-washing contains fuel oil gel deposit-forming microorganisms, and prior to said water-washing, incorporating in the wash- Water, in a microbicidal proportion of about 0.001 to 0.1

percent, an oil-insoluble, anti-microbial agent that is effective to destroy said gel deposit-forming microorganisms, said agent being selected from the group consisting of the sodium salt of 2,4,5-trichlorophenol, alkyltolylmethyltrimethylammonium chlorides whose alkyl groups contain 9 to 15 carbon atoms, and alkyldimethylbenzylammonium chlorides whose alkyl groups contain 8 to 18 carbon atoms, and after separation of the washed, treated oil from wash-water, blending the washed, treated oil with the superior of said fuel oil fractions to form a blended distillate fuel oil that approximates the superior :ofrsaidiractions with respect to;saidcharacteristic, and :that; has a reduced tendency togdeposit -gel due to agel :-deposit formingmicroorganisms.

'3. A process for refining distillate fuel oilcomprising providing at-least two fuel'oil fractions boiling -in the No.12 fuel oil;range, one of said fractions possessing a .total :acid number above about 'O.1-and the other of said fractions possessing a total acidnumber=n0t greater than about 0.1, subjecting-at least a portion of the-- fraction that has a total acid. number= above about 0.1 to an additionalrefining treatment involving first, intimate contact thereof with about 2 to 20 percent by volume of about 2 to 40 B.-aqueous caustic soda solution, separating the neutralized-fuel oil-fractionfrom ther'partially spent caustic soda solution, and-then water-washingthe oil with about 10 to 200 volume percent wash-water to remove water-solublegmaterials from the treated oil, wherein'the water used, in=at least oneofsaid'raqueous refining agent and said ---waterwa shing contains vfuelxoil .gel deposit-forming microorganisms, and, prior -to-;;said water-washing,' incorporating in .the wash-water, in a 7 microbicidal proportion of about 0.0O5-.:to 0.05 percent,

12 thesodiumsalbof 2,4,5-trichlorophenol, and after separationuofrthe washed, neutralized oil from wash-water, blending the .washed,.-neutralized oil with the fuel oil vfraction that has a, total acid, number of not greaterthan 5 about Orl,-to;form a blended distillate fuel oil thathas a total acidlnumberof not vgreater than about 0.1 and ,that haszareducedrtendency to deposit ,gel due to gel deposit-forming microorganisms.

. References, Cited in the file-of this patent UNITED STATES PATENTS 1,991,329 iMills Feb. 12,1935 2,608,522 Niehaus et a1. 'Aug. 26,1952 15 2,680,058 Harris et al. June 1 1954 OTHER REFERENCES Frear: A Catalogue of Insecticidesand Fungicides, 1948,.vol.:2,-, page142.

QReprint, from Bacteriological RevieWs,--vi;)l.- 18, No; 4,

520 December 1954, ""Microbiology in the Petroleum Industry, by Davisiet -al., pages 230 and 233 (complete article, pages 215-238). 

1. A PROCESS FOR REFINING DISTILLATE FUEL OIL, COMPRISING PROVIDING AT LEAST TWO FUEL OIL FRACTIONS BOILING IN THE DISTILLATE FUEL OIL RANGE, ONE OF SAID FRACTIONS BEING INFERIOR TO THE O THER IN AT LEAST ONE CHARACTERISTIC THAN CAN BE IMPROVED BY AQUEOUS REFINING, SUBJECTING AT LEAST A PORTION OF THE INFERIOR OF SAID FUEL OIL FRACTIONS TO AN AQUEOUS REFINING TREATMENT COMPRISING FIRST, INTIMATE CONTACT THEREOF WITH A MINOR PORTION OF A LIQUID PHASE AQUEOUS REFINING AGENT THAT IS CAPABLE OF IMPROVING THE INFERIOR CHARACTERISTIC OF THE INFERIOR FUEL OIL FRACTION, SEPARATING THE TREATED FUEL OIL FRACTION FROM THE PARTIALLY SPENT AQEUOUS REFINING AGENT, AND THEN WATER-WASHING THE OIL WITH WASH-WATER TO REMOVE WATER-SOLUBLE SUBSTANCES FROM THE TREATED OIL, WHEREIN THE WATER USED IN AT LEAST ONE OF SAID AQUEOUS REFINING AGENT AND SAID WATER-WASHING CONTAINS FUEL OIL GEL DEPOSIT-FORMING MICROORGANISMS, AND PRIOR TO SAID WATER-WASHING, INCORPORATING IN THE WASH-WATER, IN MICROBICIDAL PORTION, AN OIL-INSOLUBLE, ANTI-MICROBIAL AGENT THAT IS EFFECTIVE TO DESTROY SAID GEL DEPOSIT-FORMING MICROOGRANISMS UNDER CONDITIONS OF PH, TEMPERATURE AND NUTRITION FAVORABLE TO THEIR GROWTH, AND AFTER SEPARATION OF THE WASHED, TREATED OIL FROM WASH-WATER, BLENDING THE WASHED, TREATED OIL WITH THE SUPERIOR OF SAID FUEL OIL FRACTIONS TO FORM A BLENDED DISTILLATE FUEL OIL THAT APPROXIMATES THE SUPERIOR OF SAID FRACTIONS WITH RESPEKCT TO SAID CHARACTERISTIC, AND THAT HAS A REDUCED TENDENCY TO DEPOSITE GEL DUE TO GEL DEPOSIT-FORMING MICROOGRANISMS. 